Anti-friction coating for telescopic crane parts

ABSTRACT

The invention relates to an anti-friction coating for relatively slidable machine parts such as telescopic crane parts, in particular telescopic elements of a crane or mobile crane. A coating of anti-friction lacquer is applied to one of the relatively slidable parts, such as a telescopic crane part substrate. The anti-friction layer is compacted and sliding properties are imparted by incorporating nano-particles therein.

The invention relates to an anti-friction coating for telescopic crane parts. In particular, it relates to an anti-friction coating for telescopic elements of a crane or a mobile crane.

In the case of crane jibs, a coating of grease is conventionally used for pairs of telescopic components which slide one inside the other, and such grease has to be replaced at regular intervals by a rolling process or a spraying process. The same also applies to other pairs of sliding components or applications, for example, support systems where one element is required to slide on another in order to assume an extracted end position.

The lubricants used for this purpose are relatively expensive because they must be of a high quality and environmentally friendly. Applying the lubricant during initial assembly involves a lot of work and incurs high costs, on the one hand, and then incurs high maintenance costs for the operator on the other hand. The purpose of the lubricant is to reduce wear and resistance to friction and—as mentioned above—it has to be repeatedly replaced because the technical complexity of a permanent lubrication system is not justifiable.

Sliding component pairs used in this technical field are usually high-strength plastic components made from PA6 G, for example, on the one hand, and pre-coated fine-grained sheet steels on the other hand.

The objective of this invention is to provide an optimized anti-friction coating for telescopic crane parts. In particular, the invention provides an anti-friction for crane parts that keeps wear and resistance to friction as low as possible and does so without having to rely on a high degree of technical complexity.

The anti-friction coating for telescopic crane parts of the invention comprises a coating of anti-friction lacquer that is applied to a telescopic crane part substrate, which is compacted and to which sliding properties are imparted by incorporating nano-particles.

The substrate may be any part of a pair of sliding components. It should also be pointed out that this invention is not restricted to pairs of sliding components of telescopic jibs of a telescopic crane exclusively but may also be used with other pairs of relatively slidable components required to produce the same technical effect. One example of such pairs of components might be support members. However, the invention may be used to advantage in all other technical fields where pairs of sliding components are subjected to high stress and where there is a need to reduce wear and friction forces. For example, the invention is useful to deal with various aspects of automotive construction or in the field of mechanical construction and engineering.

Due to the nano-particles used, the invention provides a high-sheen coating which is intrinsically extremely dense and, therefore, highly resistant with good sliding properties. This significantly reduces resistance to friction and also reduces wear. Reductions of approximately 40% can be achieved in the coefficient of friction and wear can be virtually eliminated.

One particular advantage of the present invention in the field of telescopic crane design is that it enables reduction of the size of sliding components which are used in pairs. Reducing the dimensions of telescopic crane jibs is very important because reducing intrinsic weight while preserving the same strength and reliability means that an increasingly higher load can be carried. Since coefficients of friction but also the necessary design of sliding elements due to the system are also important, such as the telescopic cylinders for example, the invention also enables the load-bearing capacity of such cranes to be optimized.

The anti-friction lacquer coating of the invention can be applied to a substrate of fine-grained steel, in particular a pre-coated fine-grained steel. In one embodiment, nano-particles are incorporated as an additive on or underneath the surface of an additive layer of the anti-friction lacquer coating, in particular on a continuous basis. In one variant of this embodiment, additives with a base of siloxane are used. In this case, the surface of the anti-friction lacquer coating can be enriched with CH₃ residues, in particular on top of the silicon elements of the additive layer.

The invention will be explained in more detail below with reference to a preferred embodiment. The invention may comprise all of the described features individually and/or in any expedient combination. In the appended drawings:

FIG. 1 is a schematic view of the structure of a telescopic crane part or substrate, provided with an anti-friction coating in accordance with the invention;

FIG. 2 is a view in cross-sectional showing the lacquer surface of the anti-friction lacquer; and

FIG. 3 Is a diagram setting out the coefficient of friction and wear as a function of the number of cycles based on the prior art; and

FIG. 4 is a diagram setting out the coefficient of friction and wear as a function of the number of cycles based on the invention.

As illustrated in FIG. 1, a coated element of a pair of sliding components in accordance with the invention is based on the following structure. Disposed underneath the lacquer surface 1 is an additive layer 2. Additive layer 2 has CH₃ residues directly underneath the surface thereof and Si elements of the siloxane additive (Si) further below. The additive layer is joined to the substrate 4 by means of the siloxane bond (a regularly recurring Si—O—Si bond) denoted schematically by reference number 3. The incorporated nano-particles result in a lacquered surface which is optimized for sliding purposes. In this particular example, the substrate is the steel surface, although in practice it might be a substrate of any type.

The microscopic image of the coating film (viewed in cross-section) in FIG. 2 shows the compaction achieved by the nano-particles (siloxane additive), which leads to a smoothing of the coating film and minimizes the number and degree of irregularities. The additives are disposed continuously throughout the additive layer, thereby forming a closed film which enables a solid body to slide hydrodynamically.

As a result of the optimized anti-friction lacquer of the invention, coefficients of friction can be reduced by up to 40%, as may be seen from the two diagrams shown in FIGS. 3 and 4.

FIG. 3 shows the (mean) coefficient of friction for a pair of sliding or friction components such as known in the prior art, namely greased, pre-coated sheet steel and PA6 G plastic. The coefficient of friction is shown as a function of the number of cycles, denoted by 6, on the one hand, and the total amount of wear [micrometres] is denoted by reference number 7, on the other hand. As may be seen from FIG. 3, the coefficient of friction is, on average, in the range of approximately 0.125, while the total amount of wear increases significantly with the number of cycles and rapidly reaches a level of 400 micrometres (after 1,800 cycles).

The case of a pair of sliding components in accordance with the invention is represented in the diagram of FIG. 4. This figure is based on an anti-friction lacquer incorporating nano-particles applied to sheet steel, for which PA6 G plastic with anti-friction additives incorporated in the compound is used. The mean coefficient of friction, denoted by reference number 8, is already lower from the outset (approximately 0.07). Furthermore, this mean coefficient of friction 8 does not rise to more than approximately 0.08 after 3,600 cycles and, therefore, remains at a very practical, low value for a long service life. Wear, which is indicated by reference number 9 for the pair of sliding components in accordance with the invention, is virtually eliminated and barely moves beyond the zero line, as shown in FIG. 4. Consequently, there is virtually no wear and the anti-friction coating proposed by the invention provides an extremely long service life without having to re-lubricate constantly.

The invention having been thus described, with reference to a preferred embodiment, should not be limited to such embodiment, and is limited only by the claims herein. 

1. An anti-friction coating for telescopic crane parts, in particular telescopic elements of a crane or mobile crane, comprising a coating of anti-friction lacquer and an additive layer applied to a telescopic crane part substrate, said additive layer being compacted and incorporating nano-particles.
 2. An anti-friction coating as in claim 1, wherein the anti-friction coating is applied to a substrate comprising a pre-coated fine-grained steel.
 3. An anti-friction coating as in claim 1, wherein said nano-particles are incorporated continuously in said additive layer on or underneath the surface of the anti-friction lacquer coating.
 4. An anti-friction coating as in claim 1, comprising additives based on siloxane.
 5. An anti-friction coating as in claim 4, wherein CH₃ residues are incorporated in the surface of the anti-friction lacquer coating above the siloxane elements of the additive layer.
 6. An anti-friction coating for relatively slidable parts comprising a coating of anti-friction lacquer and an additive layer applied to at least one of said parts, said additive layer being compacted and incorporating nano-particles.
 7. An anti-friction coating as in claim 6, wherein the anti-friction coating is applied to a substrate comprising a pre-coated fine-grained steel.
 8. An anti-friction coating as in claim 6, wherein said nano-particles are incorporated continuously in said additive layer on or underneath the surface of the anti-friction lacquer coating.
 9. An anti-friction coating as in claim 6, comprising additives based on siloxane.
 10. An anti-fiction coating as in claim 9, wherein CH₃ residues are incorporated in the surface of the anti-friction lacquer coating above the siloxane elements of the additive layer. 